Suction dredging installation

ABSTRACT

In a suction dredging installation comprising a suction pipe which is connected to a pump and which has a suction mouth at its end and a throat between the pump and the suction mouth, in which the nominal flow section of the suction pipe has substantially a same value from the throat to the pump, whereas the flow section of the suction mouth is larger than said nominal flow section, the part of the suction pipe with the nominal flow section at the location of the throat is provided with a collar extending radially outwards, while the part of the suction pipe extending from the suction mouth to the throat has substantially the large flow section of the suction mouth. This shape of the suction pipe results in a toroidal supporting vortex arising before the throat which considerably reduces flow resistance.

Sept. 4, 1973 United States Patent 1 de Koning SUCTION DREDGING INSTALLATION Inventor: Jan de Koning Amsterdam Primary Examiner-Richard E. Aegerter Netherlands Assistant Exammer-Hadd Lane Attorney1mirie, Smiley, Snyder & Butrum Assignee: N.

V. Ingenieursbureau voor Systemen en Octrooien Spanstaal, Rotterdam, Netherlands Oct. 7, 1968 [22] Filed:

[21] Appl. No.: 765,421

In a suction dredging installation comprising a suction between the pump [30] Foreign Application Priority Data and the suction mouth, in which the nominal flow section of the suction pipe has substantially a same value 9 504 0 131. w W M H 05 6 56 u 61 m NB .5 I. H n n "2 n "0 m m m n e m" m ""m e N m" "w 6 m m w w m s 6 1 m 1 d L Std c 0 Umm References Cited UNITED STATES PATENTS to the throat has substantially the large flow section of 302/58 the suction mouth. This shape of the suction pipe re- 302/58 sults in a toroidal supporting vortex arising before the 302/[5 throat which considerably reduces flow resistance. 302/58 FOREIGN PATENTS OR APPLICATIONS 1,918,330 Green 3,301,606 1/1967 Bruno............

3,438,678 4/1969 Smith et a1. 661,609 11/1900 Hoover.................................

9 Claims, 5 Drawing Figures 27,674 12/1908 Great 302/58 PATENT) SE? 4 I975 INVENTOR JAN DE KONiNO TTORNEYS SUCTION DREDG ING INSTALLATION The invention relates to a suction dredging installation, comprising a suction pipe which is connected to a pump and which has a suction mouth at its end and a throat between the pump and the suction mouth, in which the nominal flow section of the suction pipe has substantially a same value from the throat to the pump, whereas the flow section of the suction mouth is larger than said nominal flow section.

Such a suction dredging installation is known. In order to reduce the inflow losses at the suction mouth, the flow section of the suction mouth has been chosen larger in the known suction dredging installation than the nominal flow section of the suction pipe, while the throat which forms the connection of the large flow section with the nominal flow section, converges gradually. It is to be remarked that reducing the inflow losses at the suction mouth of a suction pipe of a suction dredging installation is particularly important, as the inflow losses diminish the suction height of the pump.

The invention improves the afore-mentioned known suction dredging installation by the part of the suction pipe with the nominal flow section at the location of the FIG. 4 shows only the lower member of a suction pipe 33, which member is pivotally connected in a known way to a top member of this suction pipe 33, which top member is pivotably suspended from a suction dredging installation. The lower member of the suction pipe 33 mainly consists of an inner pipe 34 which is connected via the top member to a sand pump not shown and disposed, for instance, 10 m below the water-level, a jacket 35 which encloses the inner pipe 34 and is rigidly connected thereto, and a sliding pipe 37 which is mounted axially, slidably in the inner pipe 34, is driven by means of three hydraulic cylinders 36 and which has substantially about the same nominal flow section as the inner pipe 34. The sliding pipe 37 has at its lower end a pipe portion 42 of considerably larger flow section. This pipe portion 42 bears a strainer 38. The pipe portion 42 is lengthened at the end remote from the strainer 38 by a guide pipe 43 of the same diameter. This guide pipe 43 and therefore the pipe portion 42 is connected by radial butt straps 53 to portion 54 of the sliding pipe 37. This portion 54 has at the lower end a radial collar 55 which leaves free an annular gap 52 between itself and the pipe portion 42. The guide pipe 43 has an axial sliding fit in the throat being provided with a collar which extends radijacket end 39. Disposed between the lower end of the ally outwards and by the part of the suction pipe extending from the suction mouth to the throat having substantially the large flow section of the suction mouth. As a result of the thus formed throat the resistance losses are minimal, owing to a supporting vortex which arises before the throat. Producing the throat with the edge extending radially outwards is less expensive than producing a throat converging gradually.

The mentioned and other features of the invention will be illucidated in the following description of two suction pipes for suction dredging installations according to the invention, with reference to the accompanying drawings, wherein:

FIG. 1 shows a longitudinal section of a suction pipe for a suction dredging installation according to the invention,

FIGS. 2 and 3 show sections taken along the lines Il--II AND III-III of FIG. 1 respectively,

FIG. 4 shows a view of a partly cut-away lower member of a preferred embodiment of such a suction pipe and FIG. 5 shows on a larger scale the detail V of FIG. 4.

FIG. 1 shows only .a lower part of a suction pipe 1 of a suction dredging installation. The suction pipe 1 mainly consists of a pipe portion 5 with a nominal flow section A which pipe portion 5 is connected to a pump not shown, a radial collar 6 attached to the lower end of the pipe portion 5 and a pipe portion 7 connected to the collar 6, said pipe portion 7 having a flow section B which is considerably larger than the nominal flow section A. At the lower end of the pipe portion 7 a suction mouth 3 with the flow section B is provided.

In this way a throat 2 is formed between the-pipe portions 5 and 7, above which throat 2 the suction pipe 1 has a same nominal flow section A up to the pump and under which throat 2 the suction pipe 1 has a considerably larger flow section B extending from the suction mouth 3 (FIG. 2 and 3). When sucking up a suspension of sand and water a toroidal supporting vortex 4 arises before the throat 2 which vortex results in that the suspension flow passes the throat 2 without or nearly without resistance.

portion 54 of the sliding pipe 37 and the guide pipe 43 is a cylindrical space 45 connected at its top end to a cylindrical space 46 between the jacket 35 on the one hand and the sliding pipe 37 and the inner pipe 34 on the other, which latter space 46 is connected to a supply 47 of water under pressure connected to a pump, delivering water under regulatable pressure. The water under'pressure can emerge from the space 46 through the gap 52 into the pipe portion 42. The pipe portion 42 is connected to the portion 54 of the sliding pipe 37 via a throat 51. In connection with the making a hole in the sand the jacket end 39 of the suction pipe 33 has a sharp lower edge 40. As a result of the wide suction mouth 44 and the wide pipe portion 42 at the end of the sliding pipe 37 and as a result of the annular gap 52 for the admission of water under pressure, the resistance is low when flow enters into the sliding pipe 37, owing to the toroidal supporting vortex 55 which still is intensifled by the inflowing water under pressure. v

If the cylindrical space communicates with the outer water standing above the sand to be sucked up instead of with a supply 47 connected to a pump, the supporting vortex 60 drives the water emerging from the annular gap 52" round itself into the portion 54 of the sliding pipe 37. In this way the water flow from the gap 52 and the sand flow which enters through the suction mouth and the strainer 38, are guided into the portion 54 without much flow resistance.

What I claim is: I

1. Suction dredging installation comprising a suction pipe which is connected to a pump and which has a suction opening at its end and a throat between the pump and the suction opening, in which the nominal flow se'ction of the suction pipe has substantially a same value from the throat to the pump, whereas the flow section of the suction opening is larger than said nominal flow section, characterised in that the part of the suction pipe with the nominal flow section at the location of the throat. is provided with a collar which extends radially outwards, and in that the part of said suction pipe, extending from the suction opening to the throat, has substantially said large flow section of the suction opening said part of the suction pipe with nominal flow section being eclosed by a water pipe which has the same diameter as the part of the suction pipe extending under the throat and which is connected via an annular gap along the outer edge of the collar to the part of the suction pipe extending under the throat.

2. Suction dredging installation according to claim 1, characterised in that at least one pipe for water under pressure is attached to the sliding pipe, which pipe for water under pressure communicates at its lower end via the annular gap with the suction pipe.

3. Suction dredging installation comprising a suction pipe which is connected to a pump and which has a suction opening at its end and a throat between the pump and the suction opening, in which the nominal flow section of the suction pipe has substantially a same value from the throat to the pump, whereas the flow section of the suction opening is larger than said nominal flow section, characterised in that the part of the suction pipe with the nominal flow section at the location of the throat is provided with a collar which extends radially outward, and in that the part of said suction pipe, extending from the suction opening to the throat, has substantially said large flow section of the suction opening the suction pipe comprising an inner pipe, a sliding pipe disposed at the lower end of the inner pipe and telescopically co-operating therewith, a jacket enclosing the inner pipe and the sliding pipe and drive means for driving the sliding pipe, the sliding pipe having at its lower end the throat.

4. In a dredging installation for suction dredging sand and the like from beneath a body of water, the combination of:

suction pipe means presenting a suction mouth and adapted to be connected at its upper end to a suction pump so as to induct a mixture of sand and water through said suction mouth, said suction pipe means also presenting a throat between said upper end thereof and said suction mouth, said suction pipe means being of substantially uniform crosssectional area upwardly from said throat and being of substantially uniform but larger cross-sectional area from said suction mouth to said throat whereby to present an abrupt cross-sectional area reduction at said throat; and

means for introducing secondary water into said suction pipe means immediately below said throat to form vortex flow in the region of transition between said larger and smaller cross-sectional areas at said throat, whereby to minimize the inflow losses at the suction mouth.

5. In a dredging installation as defined in claim 4 wherein said suction pipe means includes an upper pipe section and a sliding pipe section extensible below the upper pipe section and presenting said throat at its lower extremity, an enlarged pipe portion fixed to said sliding pipe section and enclosing said lower extremity so as to project above and below said throat and presenting an annular passage for secondary water between the sliding pipe section and said enlarged pipe portion above said throat, a radially outwardly projecting collar fixed to said lower extremity of said sliding pipe section around said throat and defining opening means between it and said enlarged pipe section in surrounding relation to said throat, said collar defining said abrupt cross-sectional area reduction at said throat, and said annular passage and opening means forming part of said means for introducing secondary water.

6. In a dredging installation as defined in claim 5 wherein said suction pipe means also includes a jacket for secondary water surrounding said sliding pipe section and having a reduced tubular lower end portion aligned therewith and presenting said suction mouth, said enlarged pipe portion being dimensioned for close sliding fit within said reduced tubular lower end portion.

7. In a dredging installation as defined in claim 6 wherein said means for introducing secondary water includes conduit means for introducing secondary water under pressure into said jacket.

8. In a dredging installation for suction dredging sand and the like from beneath a body of water, the combination of:

an outer jacket having a reduced tubular lower end portion defining a suction mouth at its lower extremity;

a sliding pipe adapted to be connected to a suction pump, said sliding pipe having a cross-sectional area substantially smaller than the cross-sectional area of said tubular lower end portion of said jacket and defining a throat at its lower extremity;

means mounting said sliding pipe within said jacket in concentric alignment with said tubular lower end portion of the jacket;

an enlarged pipe portion fixed in concentric relation to said sliding pipe, said pipe portion extending above and below said throat to present an annular passage between it and the sliding pipe which extends above said throat and communicates with the interior of said jacket, said pipe portion being dimensioned to fit in close sliding relation within said tubular lower end portion of said jacket;

a strainer at the lower end of said pipe portion;

a collar projecting radially outwardly from the lower extremity of said sliding pipe toward said pipe portion and defining opening means therewith lying in surrounding relation to said throat; and

means for introducing secondary water into said jacket while a mixture of sand and water is flowing through said suction mouth into said throat whereby secondary water flows from said jacket through said annular passage and said opening means to form an annular vortex immediately below said collar and surrounding the area beneath said throat.

9. In a dredging installation for suction dredging sand and the like from beneath a body of water, the combination of:

suction pipe means having an open lower end presenting a suction mouth and adapted to be connected at its upper end to a suction pump so as to induct a mixture of sand and water through said suction mouth, said suction pipe means also presenting a throat between said upper end thereof and said suction mouth, said suction pipe means being of substantially uniform cross-sectional area upwardly from said throat and being of substantially uniform but larger cross-sectional area from said suction mouth to said throat; and

means defining an abrupt cross-sectional area reduction at said throat for forming an annular vortex surrounding the area immediately below said throat, whereby to minimize inflow losses at said suction mouth.

* I i i i 

1. Suction dredging installation comprising a suction pipe which is connected to a pump and which has a suction opening at its end and a throat between the pump and the suction opening, in which the nominal flow section of the suction pipe has substantially a same value from the throat to the pump, whereas the flow section of the suction opening is larger tHan said nominal flow section, characterised in that the part of the suction pipe with the nominal flow section at the location of the throat is provided with a collar which extends radially outwards, and in that the part of said suction pipe, extending from the suction opening to the throat, has substantially said large flow section of the suction opening said part of the suction pipe with nominal flow section being eclosed by a water pipe which has the same diameter as the part of the suction pipe extending under the throat and which is connected via an annular gap along the outer edge of the collar to the part of the suction pipe extending under the throat.
 2. Suction dredging installation according to claim 1, characterised in that at least one pipe for water under pressure is attached to the sliding pipe, which pipe for water under pressure communicates at its lower end via the annular gap with the suction pipe.
 3. Suction dredging installation comprising a suction pipe which is connected to a pump and which has a suction opening at its end and a throat between the pump and the suction opening, in which the nominal flow section of the suction pipe has substantially a same value from the throat to the pump, whereas the flow section of the suction opening is larger than said nominal flow section, characterised in that the part of the suction pipe with the nominal flow section at the location of the throat is provided with a collar which extends radially outward, and in that the part of said suction pipe, extending from the suction opening to the throat, has substantially said large flow section of the suction opening the suction pipe comprising an inner pipe, a sliding pipe disposed at the lower end of the inner pipe and telescopically co-operating therewith, a jacket enclosing the inner pipe and the sliding pipe and drive means for driving the sliding pipe, the sliding pipe having at its lower end the throat.
 4. In a dredging installation for suction dredging sand and the like from beneath a body of water, the combination of: suction pipe means presenting a suction mouth and adapted to be connected at its upper end to a suction pump so as to induct a mixture of sand and water through said suction mouth, said suction pipe means also presenting a throat between said upper end thereof and said suction mouth, said suction pipe means being of substantially uniform cross-sectional area upwardly from said throat and being of substantially uniform but larger cross-sectional area from said suction mouth to said throat whereby to present an abrupt cross-sectional area reduction at said throat; and means for introducing secondary water into said suction pipe means immediately below said throat to form vortex flow in the region of transition between said larger and smaller cross-sectional areas at said throat, whereby to minimize the inflow losses at the suction mouth.
 5. In a dredging installation as defined in claim 4 wherein said suction pipe means includes an upper pipe section and a sliding pipe section extensible below the upper pipe section and presenting said throat at its lower extremity, an enlarged pipe portion fixed to said sliding pipe section and enclosing said lower extremity so as to project above and below said throat and presenting an annular passage for secondary water between the sliding pipe section and said enlarged pipe portion above said throat, a radially outwardly projecting collar fixed to said lower extremity of said sliding pipe section around said throat and defining opening means between it and said enlarged pipe section in surrounding relation to said throat, said collar defining said abrupt cross-sectional area reduction at said throat, and said annular passage and opening means forming part of said means for introducing secondary water.
 6. In a dredging installation as defined in claim 5 wherein said suction pipe means also includes a jacket for secondary water surrounding said sliding pipe section and having a reduced tubular Lower end portion aligned therewith and presenting said suction mouth, said enlarged pipe portion being dimensioned for close sliding fit within said reduced tubular lower end portion.
 7. In a dredging installation as defined in claim 6 wherein said means for introducing secondary water includes conduit means for introducing secondary water under pressure into said jacket.
 8. In a dredging installation for suction dredging sand and the like from beneath a body of water, the combination of: an outer jacket having a reduced tubular lower end portion defining a suction mouth at its lower extremity; a sliding pipe adapted to be connected to a suction pump, said sliding pipe having a cross-sectional area substantially smaller than the cross-sectional area of said tubular lower end portion of said jacket and defining a throat at its lower extremity; means mounting said sliding pipe within said jacket in concentric alignment with said tubular lower end portion of the jacket; an enlarged pipe portion fixed in concentric relation to said sliding pipe, said pipe portion extending above and below said throat to present an annular passage between it and the sliding pipe which extends above said throat and communicates with the interior of said jacket, said pipe portion being dimensioned to fit in close sliding relation within said tubular lower end portion of said jacket; a strainer at the lower end of said pipe portion; a collar projecting radially outwardly from the lower extremity of said sliding pipe toward said pipe portion and defining opening means therewith lying in surrounding relation to said throat; and means for introducing secondary water into said jacket while a mixture of sand and water is flowing through said suction mouth into said throat whereby secondary water flows from said jacket through said annular passage and said opening means to form an annular vortex immediately below said collar and surrounding the area beneath said throat.
 9. In a dredging installation for suction dredging sand and the like from beneath a body of water, the combination of: suction pipe means having an open lower end presenting a suction mouth and adapted to be connected at its upper end to a suction pump so as to induct a mixture of sand and water through said suction mouth, said suction pipe means also presenting a throat between said upper end thereof and said suction mouth, said suction pipe means being of substantially uniform cross-sectional area upwardly from said throat and being of substantially uniform but larger cross-sectional area from said suction mouth to said throat; and means defining an abrupt cross-sectional area reduction at said throat for forming an annular vortex surrounding the area immediately below said throat, whereby to minimize inflow losses at said suction mouth. 